Regular Two-Dimensional Packing of Congruent Objects: Cognitive Analysis of Honeycomb Constructions

A new approach to investigate the two-dimensional, regular packing of arbitrary geometric objects (GOs),using cognitive visualization, is presented. GOs correspond to congruent non-convex polygons with their associated coordinate system. The origins of these coordinate systems are accepted by object poles. The approach considered is based on cognitive processes that are forms of heuristic judgments. According to the first heuristic judgment, regular packing of congruent GOs on the plane have a honeycomb structure, that is, each GO contacts six neighboring GO, the poles of which are vertices of the pole hexagon in the honeycomb construction of packing. Based on the visualization of the honeycomb constructions a second heuristic judgment is obtained, according to which inside the hexagon of the poles, there are fragments of three GOs. The consequence is a third heuristic judgment on the plane covering density with regular packings of congruent GOs. With the help of cognitive visualization, it is established that inside the hexagon of poles there are fragments of exactly three objects. The fourth heuristic judgment is related to the proposal of a triple lattice packing for regular packing of congruent GOs.

On lattice coverings by simplices

By studying the volumes of generalized difference bodies, this paper presents the first nontrivial lower bound for the lattice covering density by n-dimensional simplices.

Flash floods potential area mapping at Huong Khe district, Ha Tinh prov

Ha Tinh is one of the provinces most affected by natural hazards, especially flash floods. Sloping hilly terrain conditions, reduced covering density of forest and unfavorable weather conditions are potential hazards to flash floods. Flash floods potential area mapping at Huong Khe district, Ha Tinh province was carried out using Remote Sensing and GIS technologies. Factors causing flash floods was indentified and classified basing n their afecting level. Component maps of flash flood–causing factors were overlayed. Factors causing flash floods as noted by Greg Smith included: slope, soil type, forms of using land, covering density of forest. Potential areas of flash floods and the potential level of each part were indentified. The resulted maps can be used for forecasting risk regions of flash floods at the district.

The Effect of Variation Concentration Nd3+ Ions on Physical and Optical Properties of TZBN Glass

This study aims to determine the optical and physical properties of TZBN:Nd glass with the composition (mol%) 60TeO2-2Bi2O3-(34-x)ZnO-4Na2O-xNd2O3 with variation of doping x = 0.5; 1.0; 1.5; 2.0. Fabrication has been done by using the melt-quenching technique. Characterization of tellurite glass covering density, refractive index and absorption spectrum of glass. Density of glass have been measured using the Archimedes method. Refractive index of glass have been measured using the Brewster angle at wavelength 746.191 nm. Absorption spectrum measurements using UV-Vis-NIR spectrophotometer Perkin Elmer Lambda 25 in the region of 200-1100 nm. The results of characterization show that density / physical characteristics of glass did not increase when the concentration of ions Nd3+ to TZBN:Nd glass increased. The refractive index of glass will increase as the concentration of ions Nd3+ to TZBN:Nd glass increased. Based on the results of UV-Vis-NIR spectroscopy measurements shows that there are nine significant spectra have been observed in the region of 200-1100 nm, such as at a wavelength of 431 nm, 474 nm, 515 nm, 527 nm, 585 nm, 684 nm, 749 nm, 805 nm, and 878 nm and the highest absorption peak is at a wavelength of 585 nm.

Influence of Acoustic Coating on the Underwater Sound Radiation of a Double Hull Cylindrical Shell Structure

This paper studies the influence of acoustic coating to the underwater sound radiation characteristic of a double hull cylindrical shell by the Statistical Energy Analysis (SEA) method. Influence of covering density and laying location of acoustic coating to the underwater sound radiation characteristic of the double hull cylindrical shell structure are discussed. Study shows that low covering density of acoustic coating will cause “sound leaking” phenomena, sound will leak out from the uncovered area of the double hull cylindrical hull structure and radiate into the surrounding water, which harms the underwater noise reduction performance of the acoustic coating; however, the noise reduction capacity of the acoustic coating improves gradually as the covering density increases. Besides, laying location of acoustic coating also impact the underwater sound radiation performance of the double hull cylindrical shell structure; inner hull covered with acoustic coating is better than the outer hull covered from the noise treatment point of view

Transpiration of irrigated apple trees and citrus from a water potential gradient approach in the leaf-atmosphere system

The uptake of water from the roots of crops comes to being a physiological response of the plant to the water loss process through its stomata. Getting to know the daily transpiration rates throughout the phenological cycle allows for the application of the ideal amount of irrigation water at the right moment to maximize production with environmental protection. Since transpiration direct measurements at the field, mainly for trees in general, are to be of operational difficulty and relatively high cost we came up with a methodology that allows one to calculate the daily transpiration rates of apple trees and citrus orchards from variables of both the physical environment and the crop. The input data of the proposed model are air temperature, air relative humidity, photoperiod duration, and leaf area. Estimated transpiration rates based on the water potential gradient between the air and leaf approach were comparable in apple trees and citrus orchards. Sap flow daily values were obtained by means of the heat balance method at Bordeaux, France, and Piracicaba, SP, Brazil. All the coefficients of determination of the regression equations obtained herein were higher than 0.93. This allows one to calculate the amount of irrigation water to be applied throughout the crop growing seasons with a high precision as a function of meteorological data and crop covering density at the sites in the study.